Engine system components (such as cylinder valves, crankshafts, camshafts, pistons, fuel injectors etc.) may be intermittently diagnosed for damage incurred during engine operation. Diagnostics may involve visually inspecting the components for damage (e.g., misalignment or twisting), such as by removing a spark plug and obtaining a bore scope to view inside the cylinder. Damage to crankshaft and/or camshafts can lead to variability in determining their position (in order to identify engine and piston positions). As such, the position of the cams/pistons is required during an engine restart to enable coordination of the spark timing and fuel delivery in the engine. Thus, any errors in position determination can lead to reduced ability in achieving and maintaining fast synchronization, reliable combustion, and reduced emissions. Further, any delays in identifying engine position can also delay engine starting.
The inventors herein have recognized that the above discussed approaches for visually inspecting engine components can add extensive time, cost, and complexity to the diagnostics. In particular, most of the above approaches require a skilled technician, complex diagnostic tools, specialized laboratory facilities, and time consuming engine teardown. In view of these issues, the inventors have realized that in engine systems configured with laser ignition capabilities, components of the laser ignition system can be advantageously used to diagnose various engine system components.
In one example, the engine may be diagnosed by a method comprising: over an engine cycle, operating a laser ignition device in each engine cylinder; identifying a piston position in each cylinder based on the operating; and indicating degradation of an engine crankshaft based on a piston position of each cylinder. In another example, a cylinder valve position in each cylinder may be identified based on the operating; and degradation of a camshaft may be indicated based on the valve position of each cylinder. In still a further example, laser illumination based piston position measurements may be used to determine the position of a crankshaft while laser illumination based intake or exhaust valve position measurements may be used to determine the position of a camshaft. Based on the relative positioning of the crankshaft relative to the camshaft, misalignment errors may be identified.
For example, a laser ignition device may be operated at a lower power level during an intake stroke of a cylinder to rapidly direct laser pulses into a cylinder and perform a planar sweep of the cylinder. Based on a duration elapsed since the emission of the laser pulse and the detection of the laser pulse following reflection off the piston surface, the position of the piston in the given cylinder may be determined. In addition, the duration may be used to infer whether a cylinder valve is open or closed. For example, based on the elapsed duration estimated following laser pulse emission in an intake stroke, it may be determined if the intake valve is open or closed, and thereby the position of an exhaust valve may be inferred. Alternatively, based on the elapsed duration estimated following laser pulse emission in an exhaust stroke, it may be determined if the exhaust valve is open or closed, and thereby the position of an intake valve may be inferred. By comparing the piston position of each cylinder relative to one another crankshaft alignment errors may be determined. For example, by comparing the estimated position of each cylinder to the expected position of each cylinder (based on the cylinder firing order, the engine configuration, etc.), it may be determined if the crankshaft position is deviated from a home position, and crankshaft degradation due to twisting or breaking may be indicated. Likewise, by comparing the intake or exhaust valve position of each cylinder relative to one another, camshaft alignment errors may be determined. For example, by comparing the estimated position of each cylinder's intake valve, and thereby intake cam, to the expected position of each cylinder's intake valve and intake cam (based on the cylinder firing order, the engine configuration, the cylinder stroke, etc.), it may be determined if the camshaft position is deviated from a home position, and camshaft degradation due to twisting or breaking may be indicated. Further still, by comparing the estimated crankshaft position to the estimated camshaft position, misalignment errors may be determined.
In this way, engine position based diagnostics can be expedited and simplified without necessitating engine disassembly. In particular, it may be possible to use piston position and cylinder valve position estimates, as determined using an engine laser ignition system, to determine crankshaft and/or camshaft alignment errors. By taking advantage of the laser ignition system to estimate the piston and valve position, positional information can be gathered faster and more reliably. By using the positional information to diagnose the crankshaft and camshaft, the time and cost associated with the visual inspection of the components is reduced. Overall, engine inspection can be simplified without reducing inspection accuracy.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.